Pump for corrosive agents



Sept. 23, 1958 J. N. BRUCE 2,853,024

PUMP FOR CORROSIVE AGENTS Filed July 12, 195e 2 Sheetsrsheet l F/g. l,/9 x" 5 .r /a A( 27 29 /7 5 53 /a 3/ '7 s 5 /7 29 n /3 /5 27 55 l l/ls 225 25 l,

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w 'J 5 5 l 33 35 i i j 723 ,a 25 3725 la 3 /7 Y INVENTOR.

Jo/7n N. Bruce ATTORNEY Sept. 23, 1958 J. N. BRUCE PUMP FOR CORROSIVEAGENTS 2 Sheets-Sheet 2 Filed July l2, 1956 INI EN TOR. .l0/7n N. BruceBY vm/. @n

A T TORNE Y United States Patent Utilice PUMP Fok CoRRosrvE AGENTS JohnN. Bruce, Bel Air, Md., assigner to the United States of America asrepresented by the Secretary of the Army Application July 12, 1956,Serial No. 597,559

7 Claims. (Cl. ID3-148) (Granted under Title 35, U. S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment to me of any royalty thereon.

This invention relates to pumps and in particular to a plunger-diaphragmpump especially suitable for use with corrosive agents.

Leakage is a common problem encountered in pumping. Where the agent is acorrosive one this problem is greatly enhanced. Diaphragm type pumpshave been used successfully to prevent leakage when pumping highlypenetrative agents. Elastic type diaphragms have been used which arestretched by a plunger thereby changing the volume within the pumpingchamber and resulting in a pumping action. However, the constantexpansion and contraction of the diaphragm by stretching results infatigue of the material and thereby diaphragm deterioration.

It is an object of this invention to provide a diaphragm pump which canbe used to pump any tluid and in particular fluids of a corrosivenature.

It is also an object of this invention to provide a pump with a flexiblediaphragm which will not deteriorate excessively and which can employdiaphragms made of any one of numerous ilexible materials.

It is a further object to pro-vide a pump in which the cylinder unitscan be quickly and easily replaced and the capacity easily varied.

Another object of this invention is to prevent or minimize leakageproblems in a pump especially when handling corrosive agents.

Further objects and advantages of the invention will be apparent fromthe following description.

Fig. 1 is a sectional elevational view of a pump along line 1-1 of Fig.2.

Fig. 2 is a sectional plan view of the pump taken along line 2--2 ofFig. l.

Fig. 3 is a partial sectional view along line 3-3 of Fig. 2.

Fig. 4 is a partial sectional View of the plunger and diaphragm.

Fig. 5 is a plan view of the diaphragm shown in Fig. 4.

Fig. 6 is a sectional View showing a modification of the diaphragm.

Fig. 7 is a sectional view of the modication taken along line 7-7 ofFig. 6.

Referring to Figs. l and 2, the pump, generally designated as 1,comprises a body member 3 which supports t cylinder units generallydesignated as 5. The body member 3 is shown as having in internalportion 7 and external portion 9, each portion being provided with bores11 and 13 respectively for reception of the cylinder units 5. Theexternal portion 9 of the body provides added support for the cylinderunits and can be dispensed With Where such support is not required.

A cylinder unit 5 consists of an outer shell 15 and a flexible diaphragm17, having a ange 18, Welded or otherwise secured together to form aclosed cavity be- Patented Sept. 23, 1958 tween them. Fig. 4 best showsa preferred manner in which these members are joined. Suction anddischarge valves 19 are located at one end of shell 15. Such valves area common type and will not be described. The opposite end of shell 15 isthreaded internally and exteriorly. The exterior threads serve to holdthe cylinder unit in the body 3 by engaging a threaded portion of toend. The shape of the diaphragm is predicated on the fact that aperimeter of a certain length encloses the greatest area when thatperimeter is the circumference of a circle. Any other area of anothershape such as an ellipse enclosed by a perimeter of the same length issmaller. The importance of this shape will be seen further in thedescription.

The plunger assembly 21 consists of a plunger head 23 fastened to pushrod 25. A spring 27 encloses push rod 25 and extends into an opening 29in the plunger head. A spring housing 31 enclo-ses the spring and pushrod and also extends into the plunger head. Retainer nut 33 is Welded orotherwise secured to the spring housing 31. The outer surface of theretainer nut is threaded so as to engage the inner threads of shell 15.Cap 35 contains a bore through which one end of the push rod extends.The cap is threaded internally to engage a central threaded portion ofretainer 33 thereby holding the plunger assembly in place.

Pressure on the free end of push rod 25 forces the plunger into thediaphragm 17 causing its cross section to change from elliptical tocircular, thus reducing the volume in the housing cavity since thediaphragm increases its volume by having a circular cross section,which, as seen previously, has a greater area for a given perimeter thanany other area with the same perimeter. As the pressure is relieved onthe push rod, the spring 27 returns the plunger head 23 to its originalposition and the diaphragm 17 returns to its original elliptical shapethereby again enlarging the housing cavity. rThis breathing action ofthe diaphragm 17 causes the suction and discharge valve to operateproducing a flow of gas or liquid through the cylinder.

Figs. l and 2 show the pump assembly with a plurality of cylinder unitsoperated in sequence by a smooth return cam 37 mounted on drive shaft39.As the cam 37 rotates the cylinders operate consecutively causing aconstant and continuous tlow through the pump when the suction anddischarge valves are connected to conventional suction and dischargemanifolds (not shown).

The diaphragm shown in Figs. l, 2, 4, and 5 may be made of a corrosionresistant exible metal or of a ilexible metal, as spring steel, coatedwith a corrosion resistant synthetic resin.

In the modilication shown in Figs. 6 and 7 the diaphragm consists of acorrosion resistant bag 41 with a flat U-shaped spring 43 inside tocause it to recover its ellipitical cross section when the plunger iswithdrawn. This spring would also provide a wearing surtace for theplunger head 23. The bag may be made of any one of numerous materials,such as exible plastic, coated cloth, etc. This makes available a largenumber of materials, making it possible to handle a wide variety ofuids.

Since the outer shell 15 and the diaphragm 17 are welded togetherleakage cannot occur at this point or is at least kept to a minimum.However, a gasket is generally held against the flange 18 of thediaphragm 17` by retainer nut 33 in the event slight leakage occurs, asmight result from adefective weld. With the modification shown in Figs.6 and 7 a gasket is used since the corrosition resistant bag cannot bewelded to the shell.

lA completecylinder consisting of the outer shell 1S, inlet and outletvalves 19, diaphragm 17, and plunger assembly 21, forms an integralunit. Interruption of pumping operations are thereby held to a minimumby replacing a defective cylinder unit with ano-ther unit while thedefective one is being repaired. This can be done simply byshuttingoffthe suction and discharge valves from their respective manifolds,breaking connections and removing the entire cylinder unit bydisengaging the threaded shell from the threaded bore of the pump body.Then a new cylinder unit can be replaced and the connections restoredWithout affecting operation of the other cylinder units. Thus operationcontinues with only a slight decrease in capacity.

Capacity of 'the pump can be changed by varying the size of thecylinders or by varying the number of cylinder units in operation on onepump body. It can also be varied by replacing the cam, By employing camsof dif ferent configurations the plungers may be given strokes ofdifferent lengths.

Capacity can also be increased by having a series of the pump units 1driven by a common drive shaft.

'I claim:

1. A pump cylinder unit comprising an outer shell; a flexible member ofsubstantially uniform periphery throughout its length within said shelland forming a closed cavity with the walls of said shell, said flexiblemember being closed Hat at one end, open at the other end and having acircular cross section at said open end, and continuously changing shapefrom said open end to said closed end; inlet and outlet means attachedto said outer shell and communicating with said cavity; a plunger havinga leading edge and a trailing edge within said flexible member, saidplunger tapering from said trailing edge to said leading edge and havinga circular cross section at said trailing edge, and means to reciprocatesaid plunger Within said flexible member.

2. A pump cylinder unit as defined in claim l in which said flexiblemember is metallic.

3. A pump cylinder unit as dened in claim 1 in which said flexiblemember is a corrosion resistant metal.

4. A pump diaphragm comprising a lexible member of substantially uniformperiphery throughout its length, closed llat at one end, open at theother end and having a circular cross section at said open end, andcontinuously changing shape from said open end to said closed end.

5. A pump diaphragm as deiined in claim 4 in which said exible member isa corrosion resistant metallic cylinder flattened at said closed end.

6. A pump diaphragm as defined in claim 4 in which said ilexible memberis a metallic cylinder flattened at said closed end and coated with acorrosion resistant synthetic resin.

7. A pump diaphragm comprising a corrosion resistant bag ofsubstantially uniform periphery throughout its length, open at one endand having a circular cross section at said open end, closed flat at theother end and continuously changing shape from said open end to saidclosed end thereby having an elliptical shape at its midpoint, and aflat U-shaped spring within said bag,r to 'retain the shape of said bag.

References Cited in the file of this patent UNITED STATES PATENTS781,678 Richwood Feb. 7, 1905 2,322,181 Vincent June l5, 1943 FOREIGNPATENTS 861,408 France Oct. 28, 1940 1,031,480 France Mar. 18, 1953

